7 Cold Storage Systems Flashcards
list examples of simple and complex systems
simple:
- ventilated storage
- regular atmosphere storage
complex
- CA storage
- hypobaric storage
what are considered complex controls?
control of several of these:
- temp
- RH
- air velocity
- air composition
- insulation
- refrigeration cap
what are some important factors to consider for picking a storage method?
- requirements of different commodities
- consolidating of produce with similar needs to save space
- how temperature affects produce
temperature fluctuation should be ± ____°C
2
large temperature fluctuation leads to (increase/decrease) of quality
decrease
what happens if refrigeration capacity is undersized?
- slow cooling
- product warming
- large temp fluctuations
what happens if refrigeration is oversized?
wasted captial
which is preferred? one large unit or several small units?
several small units
how do you decrease temperature fluctuation?
keeping room T close to refrigeration T
(larger/smaller) surface area leads to more efficient heat transfer
larger
a _____ rate of air flow is ideal
moderate; too high and it will desiccate, too low and it won’t transfer heat efficiently
how do you prevent heat gain?
insulation
name 3 storage techniques to maintain high RH
jacketed, filacell, fog spray
describe the fog spray storage system
moisture is directly added to air stream; can make use of sonication (exfoliation using sound)
proper air circulation depends on:
- fan type and capacity
- air delivery
- package design
true or false: mass transfer is desirable
false. that’s water weight, and that decreases quality and sellable weight.
air velocity is important for maintaining _____ and establishing _____ CA condition
temperature, homogeneous
what happens in CA/MA storage?
- prevent depletion of O2
- prevent build-up of CO2 and ethylene
keep O2 at 2% (lower than normal)
keep CO2 at 5% (higher than normal)
remove ethylene
name some building materials
concrete, masonary bricks, wood frame, steel frame
name some insulating materials
fiberglass, polystyrene, polyurethane foam, urea formaldehyde
what’s used as a vapor barrier/gas seal?
polyurethane
what are the conventional refrigerated storage methods?
Jacketed and Filacell
what are the CA storage methods?
- CA generation and maintenance
- membrane systems (marcellin, atmolysair)
- hypobaric system
what are the desirable effects of CA storage?
- suppression of respiration rate
- retardation of senescence
- suppression of ethylene production
- reduction in fruit sensitivity to ethylene
- alleviation of physiological disorders
- suppression of pathogen activity
- insect control
what are the undesirable effects of CA storage?
- can promote other physiological disorders
- induce irregular ripening
- can favor development of fof flavors
- can favor stimulation of sprouting and retardation of periderm formation in some roots and tubers
what are the 2 aspects of CA/MA storage?
1) CA generation
2) CA maintenance
how is CA generation achieved?
- passive process - produce respiration
- active process - external means
what are some oxygen control systems
- recirculation/purge type
- external gas generators (open flame burners, catalytic converters)
- nitrogen generators (gas/liquid nitrogen cylinders and smit-oxydrain)
- control is ventilation (addition of O2)
what are some CO2 control systems?
- gas cylinders
- control by scrubbers like hydrated lime, water, brine water, and activated carbon/molecular sieves
what is lime?
CaOH2
what are regular atmospheric concentrations of N, O and CO2?
N = 79% O = 21% CO2 = trace
what happens to CO2 in CA storage
allowed to increase to 6% by respiration the brought down to 5%
what happens to O2 in CA storage?
allowed to decrease to 2.5% and restored to 3% by ventilation
what is the role of N2 in CA storage?
mainly filler. ~92% at maintained O2 and CO2 levels.
